Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Unrecognized tax benefits	$ 4,300		$ 4,300
Unrecognized tax benefits would impact the effective tax rate	4,300		4,300
Cumulative accrued interest	400		$ 400
Effective tax rate from operations			32.80%	36.00%
(Benefit from) provision for income taxes	(22,984)	$ (8,804)	$ (217,446)	$ (5,735)
Effective U.S corporate tax rate			21.00%				35.00%
Provision for transition tax						$ 37,200	$ 40,300
Measurement period adjustment to reduce transition tax						$ (3,100)
Transition tax, unpaid	25,100		$ 25,100
Transition Tax over an eight-year period beginning			2018
Digital asset impairment losses	65,165	44,242	$ 684,034	44,242
Tax benefit of impairment losses	191,500	12,800	191,500	12,800
Tax benefit from stock options exercise	26,000		26,000
Tax expense from stock option cancellations		$ 1,100		$ 1,100
Other Noncurrent Liabilities
Income Taxes
Unrecognized tax benefits	2,900		2,900
Transition tax, unpaid	22,100		22,100
Deferred Tax Assets
Income Taxes
Unrecognized tax benefits	1,400		1,400
Accounts Payable, Accrued Expenses and Operating Lease Liabilities
Income Taxes
Transition tax, unpaid	3,000		3,000
U.S
Income Taxes
Cash and cash equivalents and short-term investments	16,400		$ 16,400		$ 13,700
U.S | Earliest Tax Year
Income Taxes
Tax years subject to examination			2017
Italy | Earliest Tax Year
Income Taxes
Tax years subject to examination			2016
Poland | Earliest Tax Year
Income Taxes
Tax years subject to examination			2015
Spain | Earliest Tax Year
Income Taxes
Tax years subject to examination			2017
United Kingdom | Earliest Tax Year
Income Taxes
Tax years subject to examination			2017
Germany | Earliest Tax Year
Income Taxes
Tax years subject to examination			2016
Foreign
Income Taxes
Cash and cash equivalents and short-term investments	40,600		$ 40,600		46,000
Foreign earnings repatriated			57,500		$ 186,600
Undistributed foreign earnings	$ 109,500		$ 109,500